This paper first surveys three kinds of learner interview corpora (LINDSEI, NICT-JLE Corpus, and Trinity Lancaster Corpus), paying particular attention to their interview structures. Then, it explains the principles and features of the ICNALE Spoken Dialogue (ICNALE SD), which includes 425 videos and approximately 1.6-million-word transcripts of the L2 English interviews with 405 learners from ten regions in Asia and twenty native speakers. The ICNALE SD is one of the largest learner interview corpora and practically the sole dataset for the analysis of dialogue speeches by various Asian learners. As a case study based on the ICNALE SD, the author sought to find out how fluently learners in different regions speak in the interviews, which words they characteristically use, and which relationship is observed among them.